The Effects Of Hypoxia On Glycocalyx Of Glomerular Endothelial Cells In Rats

Objective: The paper is to explore impacts of high-altitude hypoxia on glomerular endothelial cell glycocalyx in rats.Methods: A total of 66 male SD rats were randomly divided into 3 groups,the control group(Xining,n=6),the hypoxia control group(5000 m;n=30)and the hypoxia drug group(dimethylthiourea,DMTU;n=30).The normoxia control group was fed in an animal room of Qinghai University Plateau Medical Research Center,while the other two groups were placed in a low pressure oxygen cabin(an oxygen concentration of 11%;an altitude of about 5000 m)to construct hypoxia animal models.Urine samples were collected at 6h,12 h,24h,48 h and 72 h from the rats,and tested with ELISA method for urine microalbumin(Um Alb)and urine creatine(Ucr)levels.Renal venous blood samples were collected from the rats after anesthesia,and tested for malondialdehyde(MDA)contents with TBA method,for superoxide dismutase(SOD)activities with WST-1 method,and for glycocalyx Syndecan-1 contents in endothelial cells with ELISA method.Kidneys were removed,and renal cortex tissues were taken and tested for glycocalyx Syndecan-1 and Glypican-1 contents in renal glomerular endothelial cells with Western Blot method.Lanthanum nitrate trace method was adopted and transmission electron microscope(TEM)was used to observe pathological changes of glycocalyx in glomerular endothelial cells of rats fed under low-oxygen environment.Results:1.After hypoxia treatment,the ratio of urine microalbumin to urine creatine(Um Alb/Ucr)started to rise at 48 h ?P<0.05.With the pharmacological intervention,the rise of Um Alb/Ucr started to present a declining trend from 48 h ?P<0.05(Table 1).2.The activity of serum SOD declined gradually with the extension of hypoxia time in the rats,while the MDA level increased gradually,P<0.05;After intervention with antioxidant,the SOD activity did not decline obviously,while there was no significant elevation of MDA level under hypoxia condition for 72h(Fig.2 &3);The SOD activity was negatively correlated with the MDA level,P<0.05(Table 5).3.Under hypoxia environment,the Um Alb/Ucr ratio in rats was negatively correlated with the SOD activity,but positively correlated with the MDA and blood Syndecan-1 levels,P<0.05(Table 5).4.Comparing with the control group,the blood Syndecan-1 level in the hypoxia control group increased with the extension of hypoxia time(P<0.05),and showed no gradual rising trend after the antioxidant intervention(P<0.05)(Fig.4).5.Comparing with the control group,the renal cortex Syndecan-1 level in the hypoxia control group increased significantly at 12 h(P<0.05),but started to decline at 24 h(P<0.05)(Table 6);The Glypican-1 level increased significantly at 24 h(P<0.05),and declined at 72h(P<0.05)(Table 6).The hypoxia drug group showed no statistical differences of Syndecan-1 and Glypican-1 levels at any time from the control group,and was statistically different from the hypoxia group(P<0.05).6.According to the pathological results,the glycocalyx layers after hypoxia treatment were characterized by a thinning trend under TEM(P<0.05),while some were deleted.After the antioxidant intervention for hypoxia,the glycocalyx layers presented no obvious change within 72 h.(Table 8).Under observation,electron microscopic sections of the three groups presented no pathology of obvious foot process fusion/disappearing,and the basilar membranes were integral without breakage.Conclusion:1.Under acute hypoxia environment,UmAlb/Ucr ratio increases gradually with the extension of oxygen-poor duration in rats,and is correlated with oxidative stress indexes,SOD and MDA.It indicates that hypoxia-induced oxidative stress can lead to early renal injury in rats.2.Under acute hypoxia condition,blood Syndecan-1 level increases gradually,and is obviously correlated with Um Alb/Ucr,suggesting that the degradation level of glycocalyx is consistent with Um Alb/Ucr ratio and,together with Um Alb/Ucr,might be a reference sign for early capillary endothelial injury.Blood Syndecan-1 level is suppressed after antioxidant intervention,indicating that anti-oxidative stress can prevent the degradation of endothelial glycocalyx.3.Blood Syndecan-1 level pr edicts early glycocalyx da mage in systematic endothelium,and antioxidant therapy is effective in protecting endothelial glycocalyx and reducing urine protein.4.Under acute hypoxia environment,the glomerular endothelial cell glycocalyx components(Syndecan-1 and Glypican-1)in a rat change with and respond to acute hypoxia environment,yet might be repaired or redistributed then.It might be consistent with the role of glycocalyx in regulating the adaptive mechanism of endothelial cell.5.Formation of rat urine microalbumin under acute hpoxia might be attributed to changed electrostatic barrier of glomerular filtration membrane caused by change of a glycocalyx layer.